Klystron



Feb. 14, 1961 G. A. E-SPERSEN KLYSTRON Filed May 25, 1959 IN V EN TOR. GEOBGEA.ESPERSEN United States Patent KLYSTRON George A. Espersen, Dobbs Ferry, N.Y., assignor to North American Philips Company, Inc., New York, N.Y., a corporation of Delaware Filed May 25, 1959, Ser. No. 815,565

4 Claims. (Cl. 3155.38)

My invention relates to klystrons.

More particularly, the invention is concerned with the reduction of noise in electron discharge tubes of the velocity modulation type, i.e. a klystron, due to frequency excursions resulting from thermal effects of anode power dissipation. Since most of the power in any klystron having two or more resonant cavities is dissipated in the output cavity, frequency excursions which occur are due to thermal effects resulting from two sources, namely the power from the electrons striking the last cone of the output resonator and the heat conducted back from the collector which receives that portion of the power from the electron beam not converted to useful radio frequency power.

It is an object of the invention to reduce noise in the output of an electron discharge tube of the velocity modulation type.

According to the invention noise due to frequency excursions resulting from thermal effects in the output of an electron discharge tube of the velocity modulation type is reduced by preventing the electron beam from striking the last cone in the output cavity and by thermally isolating the collector from the output cavity.

The invention will be described with reference to the accompanying drawing in which the sole figure shows an electron discharge tube of the velocity modulation type according to the invention.

Referring to the drawing, the klystron tube according to the invention comprises a vacuum tight envelope including a glass portion 1 enclosing an electron gun 2. The gun includes the usual heating filament 3, an electron emissive cathode 4, and focussing electrode 5. Terminals 6 for the electron gun extend through the glass envelope for connection to an external circuit.

By means of a Korvar ring 7, the glass portion 1 is sealed to the anode or resonant structure 8 of the tube. The resonant structure comprises a solid copper body 9, in which are machined a pair of resonant cavities 10 and 11. The resonant cavities communicate through a coupling aperture 12. The front side of the block is closed off by a copper plate 13 while the rear side of the block communicates with a housing 14 surrounding a collector electrode 15. A cover 16 closes the housing and is secured in place by bolts 17.

Through the centers of plates 13 and block 9 passes an aperture 18 communicating with each of cavities of 10 and 11 and serving as a path of the electron beam produced by electron gun 2. The electrons are collected by collector electrode 15. The electron beam passing through the aperture 18 communicates with the input cavity 10 by means of an interaction gap 19. In the usual way, oscillations present in the cavity 10 velocity modulate the beam as it passes across gap 19. During its subsequent passage through a drift tube 20, the beam becomes bunched in a manner well-known to the art, after which it crosses an interaction gap 21 communicating with a second or output cavity 11 producing oscillations therein. A portion of the energy is returned by ice.

way of the coupling aperture 12 to maintain the oscillation therein. A transformer section 22 communicates with the output cavity and serves as a coupling means for extracting energy therefrom. This transformer section is coupled to a member 23 adapted to have a wave-guide (not shown) secured thereto for conveying away the energy taken from the output cavity.

Since most of the noise generated in a klystron is due to frequency excursions resulting from thermal effects of power dissipation, the invention provides a means for reducing those thermal effects. One such thermal effect is the result of the electron beam striking the last cone 24 in the output cavity before entering the collector electrode 15. By making the diameter of the last section 25 of the drift tube greater than diameter of preceding section 20, the thermal elfect'of the electron beam striking cone 24 is greatly reduced.

As a further means of reducing thermal effects in the output cavity, the collector electrode is thermally insulated from the anode block by means of a metallized ceramic cylinder 26. This prevents the dissipated heat in collector 15, which constitutes about of the electron beam power, from being conducted to the output resonant cavity.

While my invention has been described in connection with a specific embodiment, other modifications thereof will be readily apparent to those skilled in the art.

What I claim is:

1. A klystron comprising an electron gun, a collector electrode, and a hollow anode between the collector and the gun, said anode defining a drift tube through which the electron beam travels toward the collector, said drift tube having two spaced portions defining an interaction gap therebetween said anode having a resonant output cavity opening onto the drift tube, the diameter of the portion of drift tube on the side of the interaction gap adjacent the collector being greater along its entire length than the diameter of the portion of the drift tube on the other side of the interaction gap.

2. A klystron comprising an electron gun, a collector electrode, and a hollow anode between the collector and the gun, said anode being thermally isolated from the collector electrode, said anode defining a drift tube through which the electron beam travels toward the collector, said drift tube having two spaced portions defining an interaction gap therebetween said anode having an output resonant cavity opening onto the drift tube, the diameter of the portion of the drift tube on the side of the interaction gap adjacent the collector being greater along its entire length than the diameter of the portion of the drift tube on the other side of the interaction gap.

3. A klystron comprising a electron gun, a collector electrode, a hollow anode between the collector and the gun, and a thermally insulating member joining said anode and collector electrode, said anode defining a drift tube through which the electron beam travels toward the collector, said drift tube having two spaced portions defining an interaction gap therebetween said anode having an output resonant cavity opening onto the drift tube, and forming a pair of cones with said drift tube, the diameter of the portion of the drift tube on the side of the interaction gap adjacent the collector being greater along its entire length than the diameter of the portion of the drift tube on the other side of'the interaction gap.

4. A klystron comprising an electron gun, a collector electrode, a hollow anode between the collector and the gun, and a tubular metallized ceramic member joining said anode and said collector electrode, said anode defining a drift tube through which the electron beam travels toward the collector, said drift tube having two spaced portions defining an interaction gap therebetween said anode having an output resonant cavity opening onto the drift tube, the diameter of the portion of the drift tube on the side of the interaction gap adjacent the collector being greater along its entire length than the diameter of the portion of the drift t be on the other sideof ,the interaction gap.

7 A ,7 "fiasaagsq References Cited in the file of this patent UNITED STATES PATENTS 2,619,611 Norton et a1 Nov. 25, 1952 2,754,448 Van Iperen July 10, 1956 2,871,397 Preist et a1. Jan. 27, 1959 2,875,369 Chambers Feb. 24, 1959 

